1. Field of the Invention
The present invention relates to computer systems and more particularly to enhancing the performance of computer systems by introducing additional processor elements.
2. Prior Art
Computer technology has been developing for the past several decades. Much of the development in the computer field has focused on optimizing computer systems in which a single processor, the central processing unit (CPU), does primarily all of the work. These optimizations have been greatly increased with the advent of integrated circuit technology. The increased power has yielded hand-held and desktop computers today that are as powerful as mainframe, room-sized computers of not more than a decade ago. In principle, the computer architecture of these new smaller computers is similar to that of the old mainframes in which a single processing unit performs all of the computer's processing operations.
One drawback of the single processor computer system is that the single processor effectively creates a bottleneck in the system thus limiting the overall speed and power of the computer. Several decades ago, a number of computer developers began developing computer systems using multiple processors. Multiprocessing systems have traditionally been more complicated to build and design as well as more expensive than the more common single processor systems. This has often been acceptable where the increased performance available from a multiprocessing system outweighs the great additional cost and hardware required to support multiprocessing. Even today in the world of very large scale integration (VLSI), multiprocessing computer systems are far more expensive and complex than single processor systems of traditional design.
Another disadvantage to traditional single processor systems is that as technology advances so quickly, they soon become, if not obsolete, sub-standard. One solution that computer developers have embarked upon is to provide an upgrade socket alongside the socket in which the integrated circuit for the central processor is plugged in. Up until now the upgrade socket has allowed for two enhancements to the computer in which it is implemented. One is to allow the addition of a specialized coprocessor integrated circuit for carrying out specialized functions on behalf of the central processing unit. Examples of such upgrades are math coprocessors and graphics processors. The other enhancement provided by an upgrade socket is to allow the substitution of a more advanced CPU integrated circuit. When a CPU chip is developed that is more powerful than the one implemented on the computer board, the enhanced processor may be plugged into the expansion socket. The computer then, upon initialization, disables the existing processor slot and treats the upgrade processor slot with the upgraded processor as the primary processor for the single processing system.
Because of the high cost of developing multiprocessing systems, this has been the limit to expandability for single processing systems. However, if it were possible to merely plug in a second processor into an upgrade socket and then have the computer system utilize both processors as a multiprocessing system, an inexpensive way to enhance a single processing system would exist. Such a system would have great cost advantages and simplicity over existing multiprocessing system, and is therefore, an object of the present invention.
For further description of traditional single processing and multiprocessing systems, see J. L. Hennessey and D. A. Patterson, Computer Architecture, A Ouantitative Approach, Morgan, Kaufman Publishers, Inc., 1990.